not trying to fight, agian, I am no automotive engineer,

but exhaust is always hot, and comparitively, intake charge is always cool...

so if that's what you want for a turbo...you get it without doing anything special.

and I thought the reason you want intake air temp to be cool, is because cool air is more dense (like me) and you get more O2 molecules in the combustion chamber...

that will produce more fire/bigger explosion, and force hotter air out the exhaust...which goes to the turbo, and pushes the turbine that much harder...

are we trying to say the same thing, but just doing it in different ways? or am I completely off the mark?

-vq

 

2kwannabe said "heat is bad". I was trying to explain to him "heat is good to run the turbine". I gave two posts about why that is.

I know cool is better for intake temps. Hence cool is better for intake charge statement.

In general we agree but you have to have heat or maintain that heat in order to get good exhaust velocity. I don't see how one would not agree with that.

 

300+ Stock HP from a I6 2.6L TT thats INSANE!.. From what I hear the true skyline that we all love is being retired... The Skyline NUR is suppose to be the last of the legends.. The US G35 will sport the skyline badges in Japan

 

So again, what happens if that charge cools? More or less velocity?

Are you sure it's not the piston going up and pushing the exhaust out and the other exhaust ports scavanging effect that's not partly the cause of the velocity? But that's a seperate subject.

 

Heating the charge after it comes out of the port probably won't do anything to increase velocity. Maintaining the heat produced is important. Again! Imagine heat flowing through a tube. Suddenly cool it down to ie. ambient. What happens?

 

That ain't shat. Subaru STIs, Mistsu EVOs, Ford Cosworth Escorts/Sierras all make a CONSERVATIVE 275-300hp from turbo 4 cylinders.

 

If it cools is not nearly as important as if it cools while under restriction. If under restriction the heat (expansion of the molecular structure of the gas) WILL contribute to velocity as long as there is a directed escape path, however if unrestricted the effect is negligible since expansion will be dissipated over all directions simultaneously if heat is the only energy in action.

Think about a smelting furnace...hot enough to melt metals and impurities but hardly like being in a hurricane if you get near one. Now let's talk tactical nuke. Again hot enought to melt metal, but the big difference is the pressure wave which levels concrete structures miles out. Is the heat making the blast wave faster? Perhaps, but it is certainly not the major player.

What caused the piston to move in the first place? COMBUSTION. Not heat. The first is an event. The second is a consequence.

 

I'm saying we agree, heat helps... Of course if the air cools it slows, that's what I'm saying about the physics of it, but I think you're overestimating the 'extra' boost of hot air. I was just trying to see what causes the velocity and I don't think it's heat. If a fluid is being supplied at a constant rate and you want to speed it up you can heat it or decrease the diameter of the conduit.

I'm saying heat helps but I don't think heat plays a major role in this, but I'm no expert. I was serious when I asked "what starts the velocity?" and this Actually it is the expansion of gases due to the combustion in the cylinder was what I was thinking.

 

All I'm saying to 2kwannabe's original statement:

He said heat is bad. I said if you don't have the heat at the turbine(ie.. maintain the heat that's produced during combustion), the exahust gas velocity is reduced.

If you just artfically heat the existing charge again(ie.. after it cools down) of course it's not going to gain velocity. That doens't make sense.

You can't get away from the heat of combustion when the charge is ignited. But you can either cool it down or try to maintain is much as possible. ie.. reason why people thermowrap the exhaust pipes( a. maintain heat b. keep the heat away from everything else)

So regardless of where/what the intial velocity comes from, if it cools down, it will slow down.

 

You may want to think about that. Ask yourself this: What caused the combustion?

 

The exchange of electrons between molecules and atoms (by definition electrically charged) resulting in the breaking of some molecular bonds and the creation of others. HEAT IS A BYPRODUCT!!!! Just like in a combustion chamber, it is the fuel, air and ELECTRICAL SPARK which start the process. Not heat!

 

I think he's referring to:
what would happen if the charge was ignited when the piston was at the bottom of the stroke? Would it even light off at all?

 

Given enough fuel, oxygen, and spark, of course. The chemical conversions would take place but not with the same explosive outward pressure. At the risk of parphrasing the layman's example from Armageddon...

...light a fircracker in your open hand, what happens? You get burned. Wrap your hand around that same cracker and light it....your wife will be opening our ketchup bottles for the rest of you life...

In much the same way C4, nitroglycerin, and other modern explosives work...they destroy things by pressure waves, not by burning them. Actual areas of heat with these explosives are rather small.

 

The electrical spark provides the heat to begin the process. Without heat the process doesn't start. The heat by-product is used to break and create the molecular bonds of others. It's a chain reaction. Heat is a by-product, but it's also needed to start the process and to continue the process.

 

Not quite. Chain reations are due to freely available electrons and other atomic and subatomic particles in the area of the chemical reaction. It is their collision with other atoms and molecules and particles and interaction of electrical charges that produces the reaction. Not that they are HOT.

 

The collisions are the result of particle velocity. Particle velocity is energy. Energy and heat are the same thing. It takes energy for these bonds to break and form. It does not happen by itself. Which is why you can mix air and gasoline togther but until you apply energy (heat) in the form of a spark or whatever, nothing happens.

 

RENNTech Mercedes Performance Tuning built a turbocharged/supercharged version of a '01 or '02 SLK 230. It was bored/stroked to 2.5L, upgraded S/C, and a small turbo (can't remember what they used) for the low end spool up. It dynoed at 380+ RWHP at 6500+ RPM. If I could only find the magazine that had that article...

Anyway, check out RENNTech's website. They might have something on it there...

RENNTech Performance

 

Time for someone to take remedial chemistry and physics.

Energy and heat ARE NOT THE SAME THING!!! Heat is a TYPE of energy. ENERGY is a generic category encompassing heat, electricity, gravity, etc, etc, etc, etc. Some types of energy can result in the generation of others, but not in all cases. Gravity can produce heat due to compression of particles and friction, but not the other way around. Electricity can produce heat depending on the reactions it starts, heat does not spontaneously create electricity.

The energy used to break bonds and create others is due to eletrical attraction/repulsion and the phyical energy of impact and collision. It is a byproduct of this activity and friction of particles that heat is generated. IT IS NOT THERE FIRST.

 

I have a master's and bachelor's degree in engineering with a minors in physics and math.

I know what you're trying to say. One correction, gravity is a force, not energy.

Which would never start in the first place unless you triggered it with heat energy.

If you don't apply heat, then how do you get the combustion to start in the first place?

I rest my case.

 

 

Hey guys here it is. The RB26DETT is one of the baddest japanese motors ever designed. It uses a twin sequential turbo system that kicks in the larger turbo after it is spooled. Its good for about 600bhp on stock internals. It can produce over 1200Hp when fully tuned to its maximum potential (R34 Veilside Street Drag). and yes hot exhaust gases traver faster spool the turbo faster and can compress more air and therefore more power.

if you have any questions on turbos and things of the such email me.

PS. Turbo is better for smaller engines that make power in higher rpm band. while superchargers are better for motors that have more power down low.

 

So you agree that exhaust velocity would be next to nil w/o the compression that the piston would provide.

 

that is exactly what I've been saying all along... and the inverse/converse/contrapositive (whatever); the heat of the exhaust contributes little (next to nil) to the spooling of the turbine. It's the velocity of the exhaust gases that's the major contributor.

 

Yes, but it's assumed that compression + combusion(explosion+expansion) = heat. So you can't get away from it. If you could take that heat away w/o losing velocity, fine. But it doesn't work that way. Take the heat away from the given above and gas velocity would slow.

Edit: Actually if you could have an combustion(gas+air+ignition) would there be any expansion of gasses?

 

jjs, the spark provides heat to combust the mixture in the cylinder... it is heat that causes combustion... without heat, nothing would happen... you could throw a lit match in the combustion chamber while the air and gasoline are compressed and the mixture will combust... it doesnt have to be a spark

 

I wonder how desiels work?

 

massive compression

 

No spark?

 

no spark... but there is the introduction of energy through the compression of the cylinder...

 

really?

 

 

Darn I missed all the fun.

 

So now that everyone is turboing there maximas, wy dont then twin turbo them?

 

Why would you want to?

 

didnt you just say that twin turbos is better because it gets rid of turbo lag.

 

Nope.

There are twin charger or dual charger systems but it doesn't apply the case you are referring to.

 

so then what is the advantage and disadvantage to using a twin turbo vs a single turbo on a maxima

 

costs/application/installation/ to name a few.

 

Advantage: can run at higher power levels with less lag and better overall responsiveness.

Disadvantage: Plumbing would be so complex on a transversely mounted FWD V6 engine that it's extremely unfeasible. Fitting one turbo is tough enough already.

A longitudinally mounted engine and RWD setup makes this much less complex and more feasible since you're clearing the transmission and drive components out of the engine bay (frees up space), and due to the fact that the longitudinal setup plumbing is easier to manage as well. Examples: Audi S4 (awd), Z32 300ZX TT rwd

 

Ok, lets take a typical hydrocarbon combustion reaction:

1 H16C7 + 11 O2 --> 8 H2O + 7 CO2

That is, 1 mol of gasoline reacts with 11 mols of Oxygen to form 8 mols of water and 7 mols of Carbon Dioxide (assuming of course a perfect world).

Now, on the left side of the reaction we have 11 mols of gas (the gasoline is a vapour and contributes next to nill to volume) and on the right side we have 15 mols of gas. Therefore the byproducts of combustion produces approximately 36% more gas resulting in a 36% increase in pressure within the cylinder (ignoring heat). This is not enough to power the engine. Where the power comes from is from the heat released by the reaction. It increases the temperature of the gases, which by our good old gas law PV=nRT, means the pressure must rise.

So in short, while some pressure is the result of the combustion products, the majority of it comes from the rise in temperature.